Fiber package comprising overlying wraps of a fibrous tape

ABSTRACT

An improved fiber package is provided wherein a dry fibrous tape is wound upon a rigid support and each overlying wrap is separated from the previous wrap by an interlay. The interlay employed in the formation of the improved fiber package possesses a stiff inner core and resilient tape contact surfaces. The fibrous tape is preferably composed of a carbonaceous fibrous material (e.g. a graphitic carbon fibrous material). The fiber package possesses enhanced stability, and is resistant to telescoping. The fibrous tape may be conveniently stored within and unreeled from the package in the absence of fiber damage.

I United States Patent [191 [1 1] 3,732,974 Ram et a1. [4 May 15, 1973 [54] FIBER PACKAGE COMPRISING 2,828,798 4/1958 Hopkins et al ..206/59 F UX 2,909,277 /1959 Thiers et al. ..206/59 A X OVERLYING WRAPS OF A FIBROUS 3,390,762 7/1968 Memicks ..206/59 F TAPE [75] Inventors: Michael J. Ram, West Orange; Primary Examiner-Leonard Summer Thomas K. Reynolds, Piscataway, Att0rneyThomas J. Morgan, Charles B. Barris both of NJ. and John A. Shelden [73] Assignee: Celanese Corporation, New York, [57] ABSTRACT N.Y. An improved fiber package is provided wherein a dry [22] Flled: 1971 fibrous tape is wound upon a rigid support and each [21] APPL 124,077 overlying wrap is separated from the previous wrap by an interlay, The interlay employed in the formation of the improved fiber package possesses a stiff inner core 206/59 C and resilient tape contact surfaces. The fibrous tape is [51] Int. Cl ..Bd /67, B32b 5/24 preferably composed of a carbonaceous fibrous [58] Field of Search ..206/59 C, 59 A, 59 R, material (e.g. a graphitic carbon fibrous material). 206/59 F, 46 FC The fiber package possesses enhanced stability, and is resistant to telescoping. The fibrous tape may be con- [56] References Cited veniently stored within and unreeled from the package in the absence of fiber damage. UNITED STATES PATENTS 2,738,176 3/1956 Hargenrater ..206/59 A 13 Chums 4 Draw F'gures BACKGROUND OF THE INVENTION In many areas of fiber technology fiber packages of a dry fibrous tape are handled and utilized.

For instance, in recent years fiber reinforced composite structures have achieved increasing acceptance. More specifically, polymer fibers as well as numerous inorganic fibrous materials, such as glass fibers, carbon fibers, boron fibers, silicon carbide fibers, aluminum silicate fibers, metallic fibers (e.g. stainless steel fibers), etc., have been incorporated in various matrix materials to provide reinforcement, and to produce composite articles. The matrix material has commonly been a thermoplastic or a thermosetting resinous material. Also, in some instances, metals have served as the matrix material.

As the fiber reinforced composite technology has developed, increasing demands have been presented for fibrous reinforcement in tape from having an appreciable length. Such relatively long lengths of fibrous material find particular use in filament winding composite formation techniques. In order to store and transport such long lengths of fibrous material prior to composite formation, it has proven convenient to wind the same upon a support, such as a bobbin or reel to form a fiber package.

However, difficulties have commonly arisen with respect to the quality of the fiber packages. For instance, it is important that substantially uniform tension be maintained across the width of the dry tape while present within the package so that it can be uniformly unwound from the package and passed directly to a tapelaying machine where it is resin impregnated and subsequently formed into a composite article. Paper interlays have been utilized in an attempt to separate adjoining wraps and to thereby attempt to maintain uniform tension across a given wrap within the package. There has been a marked tendency, however, for the contents of the package to telescope upon handling if the above objective is achieved particularly if formed of a fiber tape possessing natural lubricity, such as graphitic carbon. Also, there has been a tendency for the filaments within the fibrous material to be damaged at those locations where fiber cross-overs occur within the package.

It is an object of the invention to provide an improved fiber package comprising a continuous length of a dry tape of a fibrous material wound upon a rigid support.

It is an object of the invention to provide a fiber package of enhanced stability wherein a continuous length of a dry tape of an inorganic fibrous material is wound upon a rigid support.

It is an object of the invention to provide an improved fiber package comprising a continuous length of a dry tape of a carbonaceous fibrous material wound upon a rigid support.

It is an object of the invention to provide a fiber package which is resistant to telescoping wherein a continuous length of a dry tape of a fibrous material is wound upon a rigid support.

It is another object of the invention to provide an improved fiber package wherein substantially uniform tension is maintained across a tape of a fibrous material which is wound upon a rigid support.

It is another object of the invention to provide a stable package of a tape of a fibrous material wherein the single filament properties of the fibers present therein are substantially unimpaired.

It is a further object of the invention to provide a fiber package wherein a fibrous tape component thereof may be removed therefrom in the absence of substantial damage or loss of stability.

These and other objects, as well as the scope, nature, and utilization of the invention will be apparent from the following detailed description and appended claims.

SUMMARY OF THE INVENTION It has been found that in a fiber package comprising (a) a rigid support means, (b) a continuous length of a dry tape of a fibrous material wound in a plurality of overlying wraps about said support means, and (c) a continuous length of an interlay provided in a contiguous arrangement to said tape capable of eliminating contact between adjacent overlying wraps of said tape; that improved results are achieved if a continuous length of an interlay is provided. having a stiff inner core and resilient tape contact surfaces adjacent each side of said stiff inner core, with said stiff inner core being capable of preventing substantial transverse deformation of said interlay within said package and said resilient tape contact surfaces adjacent each side of i said inner core being capable of substantially nondeleterious engagement with said tape to form a package of increased stability.

The package of the present invention is particularly suited for handling tapes of dry carbonaceous fibers (e.g. graphitic carbon fibers).

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a fiber package in accordance with the present invention wherein a graphitic carbon tape is being wound in a plurality of overlying wraps upon a flanged bobbin.

FIG. 2 is a cross-sectional view of a portion of a preferred interlay for use in forming a fiber package in accordance with the present invention wherein the inner core thereof is Kraft paper and the tape contact surfaces thereof are tissue paper.

FIG. 3 is a cross-sectional view of a portion of a preferred interlay for use in forming a fiber package in accordance with the present invention wherein the inner core thereof is Kraft paper and the tape contact surfaces thereof are polyurethane foam.

FIG. 4 is a perspective view greatly enlarged of a twisted multifilament yarn bundle of a carbonaceous fibrous material which contains at least about percent carbon by weight and exhibits a predominantly graphitic x-ray diffraction pattern. In a preferred embodiment of the invention this yarn bundle forms the elemental unit of the fibrous tape which is provided in a fiber package in accordance with the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS The nature of the rigid support upon which the dry tape of a fibrous material is wound to form the fiber package of the present invention may be varied widely. Illustrative examples of preferred supports are bobbins, reels, spools, etc. In a particularly preferred embodiment the rigid support is a flanged bobbin or reel which is provided with a central opening capable of receiving an expandable chuck positioned upon the terminus of a variably controlled rotating shaft. The flanges of such a bobbin may be either permanently fixed or removable. For instance, frictionally engaging transparent flanges may be provided upon the bobbin while the tape is being wound upon the package which are subsequently replaced by conventional flanges once the package is formed. Such transparent flanges enable the operator to readily observe the progress of the tape winding while forming the package. The tape and interlay (described hereafter) may be initially secured to the rigid support (e.g. to its transverse axis) by any convenient technique, such as by use of an adhesive tape, glue, etc., or by an integral clamp provided upon the support.

The dry tape of fibrous material which is provided within the package of the present invention is in the form of a ribbon having an appreciable length, a substantially uniform width, and a substantially uniform thickness. The term dry tape is used herein to define a tape which has not previously undergone resin impregnation (i.e., preimpregnation) wherein a substantial portion of a resin which is to ultimately serve as the matrix of a composite article is adhering thereto. Accordingly, the surfaces of the tape are non-tacky when wound in the package. The tapes may, however, optionally be coated with a solid dry non-tacky coating (e.g., a dry resin coating) designed to serve as a finish, size, surface modifier, etc. The width and thickness of the tape are not critical provided the tape is flexible and may be wound in overlying wraps upon a support. Tape widths commonly range from about 0.5 to 8 inches, or more, and tape thicknesses commonly range from about 0.003 to 0.10 inch. The length of the tape is largely governed by the capacity of the rigid support upon which the tape is wound.

The fibrous tapes may be composed of organic or inorganic fibrous materials and may be formed by conventional techniques which will be apparent to those skilled in the art. The tapes are commonly formed from fibrous materials utilized in the formation of fiber reinforced composites. For instance, the fibrous material may be a carbonaceous fibrous material which contains at least about 90 percent carbon by weight (preferably at least about 95 percent carbon by weight). Such carbonaceous fibrous materials may be formed from either amorphous carbon or graphitic carbon. The particularly preferred inorganic fibrous material is a carbonaceous fibrous material which contains at least about 95 percent carbon by weight and exhibits a predominantly graphitic x-ray diffraction pattern. Other representative inorganic fibrous tapes are those formed from glass fiber, boron carbide fiber, silicon carbide fiber, aluminum silicate fiber, and metallic fiber (e.g. stainless steel fiber). Representative organic fibrous tapes include those formed from acrylic polymers, polyolefins, polyester, polyamides, cellulosics, etc.

In a preferred embodiment the fibrous tapes comprise a plurality of adjoining substantially parallel multifilament yarn bundles substantially coextensive with the length of the tape. Such bundles may optionally possess a twist to improve their handling characteristics, e.g. a twist of about 0.1 to tpi. If desired, a transverse weft pick may be interlaced with the yarn bundles to produce a woven tape of enhanced lateral integrity. Preferred tapes are disclosed in commonly assigned US. Ser. No. 112,189, filed on Feb. 3, 1971 of Kenneth S. Burns, George R. Ferment, and Roger C. Waugh entitled Improved Process for the Production of Carbonaceous Tapes which is herein incorporated by reference. Alternatively, the tapes may consist simply of substantially parallel continguous fiber bundles in ribbon form which include no transverse interlacement. Also, the tapes may be provided as a multifilament flat tow, or in other woven or non-woven fibrous assemblages.

The continuous length of an interlay employed in the package of the invention possesses a stiff inner core and resilient tape contact surfaces adjacent each side of the inner core. The stiff core is capable of preventing substantial transverse deformation of the interlay within the package, and the resilient tape contact surfaces are capable of a substantially non-deleterious cushioning engagement with the tape to form a package of increased stability which is resistant to telescoping. Since the interlay substantially resists transverse deformation or deflection within the package, differen tial tensions along the length of the tape and across the tape are effectively avoided which result if a portion of the tape is allowed to settle to a non-uniform degree into the interior of the package. The maintenance of uniform tension within a tape package is of prime importance if the tape is to ultimately serve as an organic polymeric fibrous precursor tape which is converted to a carbonaceous fibrous material in a thermal conversion process wherein tension is controlled. Also, if the tape within the package is to be ultimately utilized in a filament winding composite formation technique (e.g. following resin impregnation), uniform tension within the tape influences the quality of the ultimate product. For instance, in areas where relatively low tension is exerted upon a tape roping of adjoining fiber bundles, or separation of adjoining fiber bundles may occur. Additionally, damage resulting to the tape at fiber cross-over points while wound within the package is substantially eliminated since the tape is in contact solely with the resilient surfaces of the interlay.

The interlay is at least as wide as the fibrous tape, and the interlay is preferably provided in a slightly wider width than the tape, e.g. the interlay 0.1 to 0.5 inch, or more, wider than the tape.

The inner core of the interlay comprises at least one sheet of a relatively stiff stock material which possesses sufficient longitudinal flexibility to undergo smooth winding upon the rigid support. For instance, the inner core may be conveniently formed from stiff paper; plastic sheeting such as cellulose acetate, polyethylene, etc.; or metal sheeting such as aluminum foil, etc. A particularly preferred inner core is Kraft paper of about 40 to weight. The thickness of the inner core is influenced by the relative stiffness of the material selected. Commonly interlay inner cores are selected having a thickness of about 0.0025 to 0.005 inch.

The resilient tape contact surfaces of the interlay may be formed from a variety of materials. Illustrative contact surfaces include at least one ply of soft resilient paper, and soft resilient resinous materials. An example of a soft resilient paper is tissue paper of approximate weight employed in the formation of facial tissue. An example of a soft resinous material is a resilient solid foam, such as a polyurethane foam, and the like. The thickness of the soft contact surfaces can be varied, and commonly each contact surface has a thickness of about 0.002 to 0.08 inch. The soft resilient nature of the contact surfaces eliminates sliding or telescoping of a tape which is wound in a package adjacent the interlay.

The resilient contact surfaces of the interlay may be integrally bonded to the inner core or optionally provided within the package adjacent the inner core while not being attached thereto. In a particularly preferred embodiment the interlay is provided as an integral body which simplifies handling during package formation. For instance, the contact surfaces may be caused to adhere to the core by means of an adhesive, or through the use of heat bonding when the resilient contact sur' face is a resinous material. Additionally, embossing techniques may be utilized to form an integral interlay.

With reference to FIG. 1 a fiber package 1 in accordance with the present invention is shown during its formation. A flanged bobbin served as the rigid support. The pair of bobbin flanges 2 and 4 had a diameter of 12 inches, and were positioned upon a transverse axis 6 having a diameter of 6 inches. The flanges 2 and 4 were spaced 3.5 inches apart. A central opening 8 was provided within the center of transverse axis 6 and was engaged by a rotating expandable chuck (not shown). The interlay 10 had a width of 3.5 inches and is discussed below in connection with FIG. 2. The dry fibrous tape 12 had a width of 3 inches and consisted of 300 substantially parallel multifilament carbonaceous yarn bundles each having a twist of 0.5 tpi. Each bundle (13 of FIG. 4) consisted of about 400 continuous filaments having a denier per filament of about 0.7. The tape consisted of in excess of 99 percent by weight and exhibited a predominantly graphitic x-ray diffraction pattern. As the interlay 10 and tape 12 were wrapped upon the support in overlying and superimposed wraps a stable package was formed in the absence of fiber damage.

With reference to FIG. 2 the interlay 10 consisted of an inner core of 60 weight Kraft paper having a thickness of 0.004 inch, and contact surfaces 22 and 24 each consisting of 2 plys of non-perforated tissue paper wherein each ply had a thickness of 0.0025 inch.

With reference to FIG. 3 the interlay consisted of an inner core 30 of 40 weight Kraft paper, having a thickness of 0.002 inch and contact surfaces of polyurethane foam 32 and 34 each having a thickness of about 0.04 inch. The foam contact surfaces were caused to adhere to the inner core 30 by means of flame laminating.

Although the invention has been described with pre ferred embodiments, it is to be understood that variations and modifications may be resorted to as will be apparent to those skilled in the art. Such variations and modifications are to be considered within the purview and scope of the claims appended hereto.

We claim:

1. In a fiber package comprising (a) a rigid support means, (b) a continuous length of a dry tape of a fibrous material wound in a plurality of overlying wraps about said support means, and (c) a continuous length of an interlay provided in a contiguous arrangement to said tape capable of eliminating contact between adjacent overlying wraps of said tape; the improvement of providing in said package a continuous length of an interlay having a stiff inner core and resilient tape contact surfaces provided adjacent each side of said stiff inner core, with said stiff inner core being capable of preventing substantial transverse deformation of said interlay within said package and said resilient tape contact surfaces provided adjacent each side of said inner core being capable of substantially non-deleterious engagement with said tape to form a package of increased stability.

2. A fiber package in accordance with claim 1 wherein said support means (a) .is a flanged bobbin.

3. A fiber package in accordance with claim 1 wherein said continuous length of dry tape (b) comprises a plurality of substantially parallel continuous multifilament yarn bundles substantially coextensive with the length of said tape.

41. A fiber package in accordance with claim 3 wherein said yarn bundles include a twist of about 0.1 to 5 tpi.

5. A fiber package in accordance with claim 1 wherein said fibrous material of said dry tape (b) is a carbonaceous fibrous material which contains at least about percent carbon by weight.

6. A fiber package in accordance with claim 1 wherein said dry tape of fibrous material (b) is a carbonaceous fibrous material which contains at least about percent carbon by weight and exhibits a predominantly graphitic x-ray diffraction pattern.

7. A fiber package in accordance with claim 1 wherein said interlay (c) comprises an inner core of stiff paper and tape contact surfaces of tissue paper.

8. A fiber package in accordance with claim 1 wherein said interlay (c) comprises an inner core of stiff paper and tape contact surfaces of resilient solid foam.

9. In a fiber package comprising (a) a rigid support means, (b) a continuous length of a dry tape comprising a plurality of substantially parallel continuous multifilament yarn bundles of a carbonaceous fibrous material which contains at least about 90 percent carbon by weight substantially coextensive with the length of said tape wound in a plurality of overlying wraps about said support means, and (c) a continuous length of an interlay provided in a contiguous arrangement to said tape capable of eliminating contact between adjacent overlying wraps of said tape; the improvement of providing in said package a continuous length on an interlay having a stiff inner core and resilient tape contact surfaces provided adjacent each side of said stiff inner core, with said stiff inner core being capable of preventing substantial transverse deformation of said interlay within said package and said resilient tape contact surfaces provided adjacent each side of said inner core being capable of substantially nondeleterious engagement with said tape to form a package of increased stability.

10. A fiber package in accordance with claim 9 wherein said dry tape (b) is of a carbonaceous fibrous material which contains at least about 95 percent carbon by weight and exhibits a predominantly graphitic x-ray diffraction pattern.

11. A fiber package in accordance with claim 9 wherein said yarn bundles include a twist of about 0.l to 5 tpi.

12. A fiber package in accordance with claim 9 wherein said interlay (0) comprises an inner core of stiff paper and tape Contact surfaces of tissue paper.

13. A fiber package in accordance with claim 9 wherein said interlay (c) comprises an inner core of stiff paper and tape contact surfaces of resilient solid foam. 

2. A fiber package in accordance with claim 1 wherein said support means (a) is a flanged bobbin.
 3. A fiber package in accordance with claim 1 wherein said continuous length of dry tape (b) comprises a plurality of substantially parallel continuous multifilament yarn bundles substantially coextensive with the length of said tape.
 4. A fiber package in accordance with claim 3 wherein said yarn bundles include a twist of about 0.1 to 5 tpi.
 5. A fiber package in accordance with claim 1 wherein said fibrous material of said dry tape (b) is a carbonaceous fibrous material which contains at least about 90 percent carbon by weight.
 6. A fiber package in accordance with claim 1 wherein said dry tape of fibrous material (b) is a carbonaceous fibrous material which contains at least about 95 percent carbon by weight and exhibits a predominantly graphitic x-ray diffraction pattern.
 7. A fiber package in accordance with claim 1 wherein said interlay (c) comprises an inner core of stiff paper and tape contact surfaces of tissue paper.
 8. A fiber package in accordance with claim 1 wherein said interlay (c) comprises an inner core of stiff paper and tape contact surfaces of resilient solid foam.
 9. In a fiber packAge comprising (a) a rigid support means, (b) a continuous length of a dry tape comprising a plurality of substantially parallel continuous multifilament yarn bundles of a carbonaceous fibrous material which contains at least about 90 percent carbon by weight substantially coextensive with the length of said tape wound in a plurality of overlying wraps about said support means, and (c) a continuous length of an interlay provided in a contiguous arrangement to said tape capable of eliminating contact between adjacent overlying wraps of said tape; the improvement of providing in said package a continuous length on an interlay having a stiff inner core and resilient tape contact surfaces provided adjacent each side of said stiff inner core, with said stiff inner core being capable of preventing substantial transverse deformation of said interlay within said package and said resilient tape contact surfaces provided adjacent each side of said inner core being capable of substantially nondeleterious engagement with said tape to form a package of increased stability.
 10. A fiber package in accordance with claim 9 wherein said dry tape (b) is of a carbonaceous fibrous material which contains at least about 95 percent carbon by weight and exhibits a predominantly graphitic x-ray diffraction pattern.
 11. A fiber package in accordance with claim 9 wherein said yarn bundles include a twist of about 0.1 to 5 tpi.
 12. A fiber package in accordance with claim 9 wherein said interlay (c) comprises an inner core of stiff paper and tape contact surfaces of tissue paper.
 13. A fiber package in accordance with claim 9 wherein said interlay (c) comprises an inner core of stiff paper and tape contact surfaces of resilient solid foam. 